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[texts]BBC Research and Development Report Number 1968-45
R&D Report 1968-45 : The influence of the ground and the sea on medium-frequency sky-wave propagation P. Knight, R.D.C. Thoday The strength of the low-angle sky waves radiated by a medium-frequency aerial depends on the conductivity of the ground extending for many wavelengths in the direction of propagation. The field strength is greatest if the aerial radiates over open sea from the coast and falls to a limiting value as the distance between the aerial and the sea increases...
Keywords: ground; aerial; loss; inland; propagation; field; vertical; aerials; sea; strength; vertical aerials; vertical aerial; ground loss; fresnel zone; field strength; vertical radiation; earth curvature; short vertical; sky wave; effective ground
Downloads: 40
[texts]BBC Research and Development Report Number 1983-10
R&D Report 1983-10 : The design of the prototype LS5/9 studio monitoring loudspeaker. K.E. Randall, C.D. Mathers The prototype of a new medium-power studio monitor is described which is physically small enough to be accommodated in areas where a large high-power monitor would be inappropriate. The main design and performance features are as follows:- A vented cabinet having a volume of 28 litres (1 cubic foot)...
Keywords: loudspeaker; unit; frequency; sound; diaphragm; drive; bbc; profile; crossover; prototype; sound level; pressure level; drive unit; drive units; sound pressure; studio monitoring; frequency splitting; monitoring loudspeaker; sound quality; harmonic distortion
Downloads: 136
[texts]BBC Research and Development Report Number 1971-15
R&D Report 1971-15 : Low-frequency sound absorbers A.N. Burd Abstract Membrane low-frequency absorbers have been used for many years in the BBC for the absorption of low-frequency sound. A variant of this type of absorber using a compound panel had some success, but careful choice of the size and shape was necessary to obtain the optimum performance. Simplifications in the construction of perforated absorbers have led to a cheaper and more easily reproducible prefabricated form.
Keywords: absorbers; absorber; impedance; measurements; studio; membrane; reverberation; absorption; studios; hardboard; deep air; reverberation time; impedance measurements; absorption coefficients; air space; sound absorbers; low frequencies; department report; reverberation room; measured impedance
Downloads: 35
[texts]BBC Research and Development Report Number 1960-26
R&D Report 1960-26 : Visit to USA, August 7th - 28th 1960. A.V. Lord This report outlines the information and impressions concerning these topics gained during a three-work tour, which included visits to a number of USA organisations whose interest in such subjects was either known or considered highly likely. The report also includes information obtained concerning matters which, although unrelated to the subjects listed above, are known to be of interest within the Engineering Division.
Keywords: tubes; tube; mesh; storage; output; television; recording; ampex; signal; recorder; magnetic recording; camera tubes; storage tubes; time modulation; storage mesh; thermoplastic recording; television signal; recorder output; standards conversion; view storage
Downloads: 19
[texts]BBC Research and Development Report Number 1969-27
R&D Report 1969-27 : Colour camera line-up equipment J.R. Sanders The equipment described was developed to reduce the time required to achieve correct adjustment of cameras which could not be lined up very accurately in a limited space when suitable monitoring facilities were not available. The equipment is small and relatively cheap so that it can quite easily be added to existing installations, such as colour outside broadcast vehicles.
Keywords: equipment; camera; picture; monochrome; signal; signals; colour; switching; oscilloscope; udc; switching rate; picture monitor; colour camera; electronic switch; department report; monochrome picture
Downloads: 27
[texts]BBC Research and Development Report Number 1974-26
R&D Report 1974-26 : Quadraphony: Techniques involved in four channel recording and reproduction D.J. Meares A series of tests has been carried out, and recordings made, to identify some of the problems that will be encountered in recording and reproducing quadraphonic programme material. Various microphone and loudspeaker arrangements have been evaluated with the main aim of re-creating, in the listening room, the acoustic qualities - ambience, spaciousness, etc...
Keywords: quadraphonic; loudspeakers; microphones; listening; recording; cardioid; recordings; microphone; listener; quadraphony; microphone techniques; microphone configurations; listening position; channel recording; listening room; quadraphonic square; techniques involved; quadraphonic recordings; acoustic treatment
Downloads: 31
[texts]BBC Research and Development Report Number 1974-36
R&D Report 1974-36 : A fixed-tuned medium-wave receiver suitable for a road traffic information service D.E. Susans This report describes a medium-wave fixed-tuned receiver intended for use in a motorcar for the reception of a road traffic information service. Its main features are long-term tuning stability, good automatic gain control over the working signal-level range, and a carrier-level-operated muting circuit to suppress the output on weak input signals...
Keywords: receiver; mute; circuit; input; amplifier; traffic; output; muting; traffic service; khz; muting circuit; mute threshold; road traffic; volume control; integrated circuit; signal level; receiver suitable; input signal; field strength
Downloads: 39
[texts]BBC Research and Development Report 1957-14 : Television service - Isle of Man - G.I. Ross, C.J. White, D.W. Taplin, J. Hall, I. Rhodes
R&D Report 1957-14 : Television service - Isle of Man. G.I. Ross, C.J. White, D.W. Taplin, J. Hall, I. Rhodes The problem of providing the Isle of Man with a television service in Band I is discussed. It is shown that the west coast of the Island, including Peel, receives a satisfactory service from Divis and the northern sector, including Ramsey, will receive a satisfactory service from the proposed transmitter at Sandale...
Keywords: snaefell; transmitter; strength; field; divis; interference; sandale; douglas; aerial; contours; median field; ground exceeded; field strength; sea scatter; receiving sites; holme moss; field strengths; west coast; port erin; sandale transmitter
Downloads: 35
[texts]BBC Research and Development Report 1955-06 : The service area of the temporary television transmitter at Redmoss, Aberdeen - L.F. Tagholm, G.I. Ross, R.S.A. Sandell
R&D Report 1955-06 : The service area of the temporary television transmitter at Redmoss, Aberdeen. L.F. Tagholm, G.I. Ross, R.S.A. Sandell This report shows that the temporary transmitter at Radmoss, near Aberdeen, provides the city of Aberdeen with a reasonable television service using an effective radiated power of 3 watts. It is shown that the service will, in general, be similar to that expected from the final transmitter at Meldrum.
Keywords: transmitter; aberdeen; temporary; redmoss; strength; vision; field; watts; field strength; expected; temporary transmitter; service area; permanent transmitter; television transmitter
Downloads: 49
[texts]BBC Research and Development Report 1957-13 : The construction and design of dichroic mirrors - K. Hacking
R&D Report 1957-13 : The construction and design of dichroic mirrors K. Hacking The somewhat stringent optical performance of beam-splitting dichroic mirrors imposed by three-colour television can be satisfactorily achieved with present-day apparatus and techniques for preparing multilayer interference films. A guide to the design and performance of such mirrors is afforded by considering the effects of the several physical parameters in idealized systems of layers...
Keywords: layer; layers; reflection; thickness; dichroic; mirrors; wavelength; transmission; optical; amplitude; refractive indices; dichroic mirror; optical thickness; resultant amplitude; dichroic mirrors; reflected wave; normalised reciprocal; reflection coefficient; spectral response; single layer
Downloads: 47
[texts]BBC Research and Development Report Number 1965-06
R&D Report 1965-06 : Performance of 10 to 1 zoom lens for image orthicon format: (Type 10 x 35B No. 1095308). K.J. Wright The characteristics of the redesigned zoom lens type 10 x 35B have been measured. These include modulation transfer function, vignetting, transmission and veiling glare and geometrical distortion. An overall assessment based on sharpness and vignetting is given, and comparisons are made with production lenses type 10 x 35B and with other zoom lenses.
Keywords: lens; focal; aperture; zoom; length; varotal; transfer; modulation; spatial; distortion; test object; geometrical distortion; modulation transfer; transfer curves; focal length; veiling glare; subjective assessment; zoom lens; lens aperture; curves focal
Downloads: 27
[texts]BBC Research and Development Report Number 1962-41
R&D Report 1962-41 : The Sennheiser Type MD 82 and Electrovoice Type 642 microphones. W.I. Manson The Sennheiser type MD 82 and Electrovoice type 642 are both directional microphones in which sound is received through openings along a narrow tube. Type MD 82, a number of which are in use in the Corporation, is no longer in regular production but is included in this report for comparison with the currently available type 642...
Keywords: type; microphone; frequency; microphones; directivity; electrovoice; impedance; bass; sennheiser; output; frequency characteristics; directivity patterns; bass cut; sennheiser type; electrovoice type; response curves; axial frequency; switch set; cut switch; sound incident
Downloads: 59
[texts]BBC Research and Development Report Number 1987-14
R&D Report 1987-14 : Improvements to a UHF rebroadcast television link suffering tidal fading: Countisbury UHF relay station. J.H. Moore The Countisbury UHF relay station serves the localities of Lynmouth and Lynton in Devon. For some time, the problems of co-channel interference and tidal fading have on occasion been evident. The report gives results obtained utilizing a new Rebroadcast Link (RBL) antenna array, which has improved very considerably the quality of signals received at this relay ...
Keywords: channel; array; antenna; countisbury; strength; relay; bbc; picture; phased; grade; video cassette; rebroadcast link; field strength; phased array; antenna array; phased antenna; impairment grade; relay station; uhf relay; mynydd bach
Downloads: 47
[texts]BBC Research and Development Report Number 1966-24
R&D Report 1966-24 : Re-radiation from masts and similar obstacles at radio frequencies P. Knight Transmissions from v.h.f. and u.h.f. aerials may be distorted by re-radiated signals if tall obstacles such as masts or towers are situated in the service area. The amplitudes of these re-radiated signals are governed by factors discussed in this report.
Keywords: obstacle; aerial; cylinder; reflexion; field; phase; values; coefficient; equation; radiation; relative phase; power density; field strength; receiving aerial; circular cylinder; scattered power; stay wire; transmitting aerial; reflexion coefficient; direct radiation
Downloads: 33
[texts]BBC Research and Development Report Number 1986-10
R&D Report 1986-10 : Development of Slide File -- a digital store for TV stills. M. Weston Slide File is designed to take the place of slide scanners in studios as the prime source of broadcast captions and still pictures. It stores still pictures in electronic digital form and enables them to be selected for transmission by a simple 'cut' or crossfade operation. Such a store provides a convenient means of handling still pictures generated using new electronic techniques as well as handling pict...
Keywords: data; disc; store; pictures; stills; digital; picture; control; computer; input; small pictures; control computer; slide file; control panels; stills store; control panel; winchester disc; disc drive; system bus; streaming tape
Downloads: 35
[texts]BBC Research and Development Report Number 1986-13
R&D Report 1986-13 : VHF-FM radio broadcasting: tests to compare horizontal, vertical and mixed polarisations. G.H. Taylor, D.S. Cox The BBC is re-engineering its VHF-FM radio networks from horizontal to mixed polarization. This Report describes tests carried out to monitor this change and which confirm the advantages of mixed polarization. Tests from the BBC transmitting station at Wenvoe to compare vertical and horizontal polarization are described...
Keywords: antenna; multipath; polarized; receiving; wrotham; signal; antennas; polarization; reception; horizontal; received signal; polar diagrams; receiving antenna; wing mounted; horizontally polarized; multipath interference; signal strength; mixed polarized; polarized receiving; vertically polarized
Downloads: 51
[texts]BBC Research and Development Report Number 1979-10
R&D Report 1979-10 : 'CARFAX' traffic information service: requirements for the receiver. M.E. Bailey This Report discusses the design requirements for receivers for the proposed BBC 'CARFAX' Traffic Information Service. Reference is made to a BBC prototype receiver design which serves as an example.
Keywords: receiver; signal; aerial; carrier; khz; conventional; audio; splitter; radio; output; radio receiver; ordinary listening; car radio; turns swg; finish signal; signal level; conventional radio; input signal; start signal; performance requirements
Downloads: 41
[texts]BBC Research and Development Report Number 1977-39
R&D Report 1977-39 : Direct satellite broadcasing: intermodulation between multiple FM sound subcarriers. M.J. Kallaway The report describes an experimental study of the effects of intermodulation between multiple fm sound subcarriers. Such a system could provide supplementary sound channels for satellite broadcasting, where the subcarriers would frequency-modulate a 12 GHz carrier. The report concludes that a system using twelve fm sound subcarriers is very sensitive to intermodulation...
Keywords: subcarrier; subcarriers; mhz; deviation; signal; carrier; intermodulation; frequency; amplitude; multiple; sound channels; peak deviation; main carrier; intermodulation products; multiple subcarrier; subcarrier system; level comparator; subcarrier signal; frequency deviation; satellite broadcasting
Downloads: 27
[texts]BBC Research and Development Report Number 1977-23
R&D Report 1977-23 : Metal halide discharge lamps: the measurement of intensity ripple and a note on the operation at high supply frequencies. E.W. Taylor Details of the equipment used to measure the variations of light intensity ('intensity ripple') from metal-halide discharge lamps are discussed, and an estimate of the accuracy of the ripple ratio values derived from the measurements is given. The assessment of the "safe" lamp supply frequency, above which the effects of intensity ripple on fi...
Keywords: lamp; ripple; supply; waveform; exposure; ratio; ballast; frequency; safe; voltage; shutter angle; intensity ripple; lamp supply; camera frame; supply frequency; ripple waveform; frame frequency; ripple ratio; safe lamp; supply frequencies
Downloads: 33
[texts]BBC Research and Development Report Number 1977-03
R&D Report 1977-03 : Factors in the design of loudspeaker cabinets. H.D. Harwood, R. Matthews The mechanical properties of timber, wood products and other materials potentially suitable for the construction of loudspeaker cabinets have been measured and details of the results are given. Various commercially available damping materials have also been assessed and their relative efficiencies are listed...
Keywords: loudspeaker; damping; cabinet; materials; frequency; grain; material; modulus; elastic; resonance; loudspeaker unit; glass reinforced; elastic modulus; loudspeaker cabinets; damping material; sound pressure; panel damping; outer grain; relative response; reinforced plastic
Downloads: 60
[texts]BBC Research and Development Report Number 1965-44
R&D Report 1965-44 : Graphical solution of cubic and quartic equations. J.W. Head Given any cubic or quartic equation with real coefficients, it can b transformed by a change of variable into a standard form, and thus solved by means of a double-sided scale (Fig. 1) in the case of a cubic, or by means of the nomogram cases where high accuracy with this nomogram is difficult to obtain are also discussed...
Keywords: equation; quartic; equations; quadratic; nomogram; graphical; cubic; approximation; roots; accuracy; graphical solution; quartic equation; hand side; quadratic factors; left hand; mathematical report; linear interpolation; real root; quartic equations; quadratic factor
Downloads: 36
[texts]BBC Research and Development Report Number 1977-37
R&D Report 1977-37 : Improvements to cheap loudspeakers H.D. Harwood, R. Matthews The sound quality of portable domestic audio equipment is limited mainly by the loudspeaker and cabinet. An investigation has been made to determine whether, at negligible extra cost, worthwhile improvements can be made. It is concluded that in some cases, small but worthwhile improvements are possible.
Keywords: unit; loudspeaker; type; elliptical; khz; sound; bare; cone; treated; damping; circular unit; cheap loudspeakers; sound quality; loudspeaker unit; speech music; high frequency; treated type; elliptical unit; music speech; untreated elliptical
Downloads: 40
[texts]BBC Research and Development Report Number 1977-29
R&D Report 1977-29 : The HMI 575-watt metal-halide discharge lamp: measurements and predicted effects of intensity ripple using sinusoidal lamp excitation. E.W. Taylor A description is given of measurements of the light intensity ripple characteristics shown by the Wotan HMI 575-watt metal-halide discharge lamp as manufactured by Osram BmbH, Germany, when excited from a sinusoidal power source at various frequencies in the range 50Hz-2KHz...
Keywords: ripple; lamp; frequency; supply; shutter; camera; ratio; iii; intensity; dissipated; shutter angles; picture luminance; ripple ratio; frame frequency; supply frequency; intensity ripple; supply frequencies; camera frame; lamp supply; iii iii
Downloads: 36
[texts]BBC Research and Development Report Number 1968-08
R&D Report 1968-08 : The assessment of noise in audio-frequency circuits W.K.E. Geddes Experiments have been carried out to determine the signal-to-noise ratio to be aimed at in programme channels and to compare the methods of noise measurement used or proposed by various broadcasting organisations. First, subjective tests were undertaken to establish the maximum level at which various types of noise can exist in an audio-frequency circuit without producing impairment...
Keywords: noise; meter; noises; weighting; subjective; monophonic; ppm; tests; programme; impulses; listening levels; impulsive noises; white noise; sound level; weighting network; weighting networks; listening room; subjective tests; noise level; studio output
Downloads: 52
[texts]BBC Research and Development Report Number 1992-14
R&D Report 1992-14 : Building penetration loss measurements for DAB signals at 211 MHz. J.A. Green Digital Audio Broadcasting is being considered as a future method of transmitting radio programmes to the public. Some of the advantages of DAB over conventional Frequency Modulation (FM) include its resistance to multipath and its ruggedness in the presence of interference. Because of these qualities it is ideally suited for reception by mobile and portable receivers...
Keywords: field; strength; measurements; dab; location; ground; penetration; floor; measured; noise; minimum field; field strengths; field strength; location field; ground floor; standard deviations; transmitters radiating; penetration loss; building penetration; bit error
Downloads: 38
[texts]BBC Research and Development Report Number 1988-07
R&D Report 1988-07 : Polarisation converters for a DBS flat-plate antenna. M.C.D. Maddocks, D.H. Boardman The introduction of a direct broadcast by satellite television service requires suitable receiving antennas to be available. A polarisation converter and an array of linearly-polarised elements have been found to be the most suitable way of receiving the circularly-polarised radiation that would be transmitted by a DBS satellite...
Keywords: polariser; antenna; axial; ratio; radiation; spacing; polarisation; array; broadside; dbs; polarisation converters; insertion loss; axial ratio; slewed main; electric field; polariser spacing; three types; construction techniques; radiation pattern; field vector
Downloads: 36
[texts]BBC Research and Development Report Number 1969-46
R&D Report 1969-46 : Hybrid-pulse coding: Experimental equipment for tests with video signals P.C.J. Hill, R.J. Packer Hybrid-pulse coding (h.p.c.m) is a method of coding a baseband signal into a moderately wideband channel in order to improve the noise performance of a signal-processing and transmission systems. Previous Research Department Reports (Nos. Click 1969/40 and Click 1969/45) describe the principles of this coding system in some detail and also give the results obtained with experi...
Keywords: signal; digital; analogue; multilevel; coder; experimental; waveform; decoder; signals; hybrid; multilevel digital; hybrid coder; experimental equipment; digital component; hybrid decoder; video signals; regenerated multilevel; analogue signal; department report; difference signal
Downloads: 33
[texts]BBC Research and Development Report Number 1974-13
R&D Report 1974-13 : Walsh-Hadamard transformation of television pictures R. Walker, C.K.P. Clarke This report gives a summary of the basic theoretical background of Walsh-Hadamard transformation and describes a method by which the process may efficiently be carried out on real-time television signals. The use of such a transformer, augmented by signal measurements carried out in non-real time, is described...
Keywords: transform; bits; transformer; transformation; matrix; inverse; walsh; hadamard; vector; input; input vector; hadamard transformation; sparse matrices; fast transform; walsh spectrum; spectrum analyser; bit rate; shift register; television pictures; hadamard matrix
Downloads: 28
[texts]BBC Research and Development Report Number 1981-13
R&D Report 1981-13 : Planning standards for v.h.f. and u.h.f. receiving aerial discrimination and height gains at domestic receiving locations. C.P. Bell, R.I. Black This report summarizes the results of a limited investigation to study the validity of existing standards used in frequency planning of broadcast services for the protection afforded by the characteristics of receiving aerials against interfering transmissions...
Keywords: discrimination; ccir; band; receiving; directivity; relative; polarization; aerial; horizontally; locations; polarization discrimination; height gains; receiving aerial; discrimination band; aerial discrimination; band iii; ccir report; angle relative; main response; directivity protection
Downloads: 30
[texts]BBC Research and Development Report 1954-39 : The Nordwestdeutscher Rundfunk-Hiller electrostatic microphone Type M59 - J.R. Chew, D.E.L.Shorter
R&D Report 1954-39 : The Nordwestdeutscher Rundfunk-Hiller electrostatic microphone Type M59. J.R. Chew, D.E.L.Shorter The M 59 is an electrostatic microphone of exceptionally small size and of nominally cardioid polar characteristics. Tests on a single specimen are described in this report. Frequency characteristics and figures for sensitivity, noise level and interference from magnetic fields are given, together with the results of a listening test.
Keywords: frequency; microphone; electrostatic; baffle; sound; interference; magnetic; characteristics; cardioid; output; microphone head; axbt microphone; frequency characteristics; noise level; electrostatic microphone; microphone type; sound incident; magnetic fields
Downloads: 38
[texts]BBC Research and Development Report Number 1966-53
R&D Report 1966-53 : Transmitting aerial for the Bexhill VHF television station D.W. Osborne, R.D.C. Thoday, J.P. Crean The Bexhill relay station came into operation on 21st March 1966. It provides a television service to Bexhill only.
Keywords: aerial; transmitting; horizontal; bexhill; reflector; templet; band; dipole; radiation; udc; transmitting aerial; receiving aerial
Downloads: 29
[texts]BBC Research and Development Report Number 1995-09
R&D Report 1995-09 : A television colorimetry: A tutorial for system designers. A. Roberts This Report was written primarily for use as a colorimetry tutorial for any MPEG users who may feel confused by the plethora of descriptive data contained in the MPEG data-stream. It is not intended to be an exhaustive treatise on basic colorimetry or even on television colorimetry; that would require a very much larger document...
Keywords: signals; luminance; matrix; chroma; primaries; camera; linear; colour; display; equations; rgb signals; chromaticity coordinates; power law; luma signal; chroma signals; transfer characteristic; linear rgb; transfer characteristics; channel signals; matrix gamma
Downloads: 39
[texts]BBC Research and Development Report Number 1966-73
R&D Report 1966-73 : Pulse sound: A system of television sound broadcasting using pulses in the video waveform J.R. Sanders A method of including the sound signal within the video waveform is described which has the advantage that a separate sound transmitter is no longer required; the elimination of the sound transmitter allows the full bandwidth of any radio-frequency channel to be used by the vision transmission...
Keywords: pulse; pulses; sound; audio; signal; decoder; frequency; waveform; modulation; ratio; spurious sound; impulsive interference; sound pulses; video waveform; sound pulse; television sound; black level; noise ratio; pulse sound; trailing edge
Downloads: 28
[texts]BBC Research and Development Report Number 1974-37
R&D Report 1974-37 : Digital video: Some bit-rate reduction methods which preserve information in broadcast-quality digital video signals D.F. Reid PCM digital video-signals require a very high bit rate and for economic reasons particularly in transmission, it is desirable to minimise the required bit rate. Methods for reducing the bit rate fall into two main categories; (a) those methods which remove information to which the human eye is insensitive, and (b) those which exploit the redundancy o...
Keywords: entropy; code; reversible; digital; coding; signal; probability; coder; video; signals; code word; difference samples; digital video; reversible coder; bit rate; buffer store; basic compressor; reversible coding; video signals; probability density
Downloads: 35
[texts]BBC Research and Development Report Number 1993-15
R&D Report 1993-15 : Final Report of RACE Project 1036: WTDM Broadband Customer Premises Network. A. Oliphant, C.D. Mathers Discussions in 1985 with BBC Television showed that signal routeing in broadcasting centres presented two problems which would become more severe in the future: first, the increasing requirement for all sources to be available at all destinations, and second, the impending proliferation of signal standards (e.g...
Keywords: optical; laser; broadband; project; wtdm; race; demultiplexer; wavelength; coupler; bbc; broadband customer; premises network; test bed; broadband cpn; customer premises; ibcn interface; wtdm broadband; final test; star coupler; europe limited
Downloads: 52
[texts]BBC Research and Development Report Number 1970-24
R&D Report 1970-24 : Field-store standards conversion: Amplifiers for ultrasonic quartz delay lines R.V. Harvey A field store standards converter has been built which uses fused quartz delay-lines as the storage medium for the television signal. Amplifiers are required in order to recover the considerable losses in these delay-lines; the design of these amplifiers is described with reference to the choice of the parameters of the system chosen for signal transmission and to the properties of the...
Keywords: delay; input; amplifier; bandwidth; quartz; circuit; output; transducer; amplifiers; ultrasonic; input transducer; field store; delay lines; department report; input amplifier; matching network; standards converter; store standards; quartz delay; transducer capacitance
Downloads: 28
[texts]BBC Research and Development Report Number 1964-07
R&D Report 1964-07 : Effect of fabric coverings on the sound absorption of porous materials A.N. Burd Measurements have been carried out by the reverberation room method to determine the effect of fabric coverings on the sound absorption of porous backing materials. It is hoped that it may prove possible in the future to predict the behaviour of materials from measurements on small samples.
Keywords: fabrics; absorption; resistance; fabric; backing; materials; measurements; flow; high; stretched; high resistance; backing material; flow resistance; absorption coefficients; surface density; fabrics stretched; low flow; heavy fabrics; high flow; resistance backing
Downloads: 43
[texts]BBC Research and Development Report Number 1975-32
R&D Report 1975-32 : LF and MF propagation: An approximate formula for estimating sea gain. P. Knight The strength of waves propagated via the ionosphere at LF and MF may be increased if either path terminal is situated near the sea. This increase, which is known as sea gain, depends both on the distance of the terminal from the coast and on the extent of the sea beyond the coastline. An approximate formula is derived for estimating sea gain for all geographical situations which are likely to be...
Keywords: sea; terminal; gain; radiation; inland; ccir; formula; distance; path; approximate; path length; inland terminal; sea gain; path difference; ground conductivity; estimating sea; ccir report; radiation angle; approximate formula; finite width
Downloads: 32
[texts]BBC Research and Development Report Number 1980-07
R&D Report 1980-07 : Crystal Palace Band II tests: comparison of transmitted polarizations. J.H. Causebrook A description is given of an experiment conducted in the London area, with a test transmitter at Crystal Palace, to examine the relative merits of different polarizations for Band II FM radio broadcasts. The tests allowed for reception at roof-top level, in cars, and on portables. The relative amounts of multipath were assessed...
Keywords: vertical; aerial; reception; horizontal; receiving; aerials; transmitter; polarization; field; multipath; receiving aerials; field strength; receiving aerial; relative merits; car reception; receiving installation; service areas; crystal palace; department report; test transmitter
Downloads: 29
[texts]BBC Research and Development Report Number 1968-35
R&D Report 1968-35 : Airborne sound insulation requirements in studio centres T.J.B. Smith, C.L.S. Gilford This report assembles data on the sound power levels of various sources of interference, including studios and other technical areas, and on the permissible levels of noise in all parts of a studio centre. From these data, curves showing the required attenuation between sound sources and all types of broadcasting area are derived...
Keywords: sound; studio; curve; studios; partition; levels; noise; reduction; criterion; insulation; required reduction; echo rooms; sound reduction; reduction requirements; sound pressure; drama studio; sound insulation; pressure levels; background noise; sound level
Downloads: 29
[texts]BBC Research and Development Report Number 1963-07
R&D Report 1963-07 : Experiment in colour television transmission to the USA by Telstar satellite H. Page, D.E. Todd The BBC was asked in July 1962 to provide colour television signals to GPO for an experimental transmission to the USA by the Telstar satellite. This report summarises this experiment.
Keywords: telstar; colour; goonhilly; frequency; receiver; doppler; satellite; subcarrier; transmission; pass; colour subcarrier; experimental transmissions; colour television; subcarrier frequency; telstar satellite; received subcarrier; loop circuit; television transmission; colour receiver
Downloads: 36
[texts]BBC Research and Development Report Number 1976-22
R&D Report 1976-22 : Satellite broadcasting: Optimal distribution of frequency channels, orbital positions and polarisations. R.V. Harvey The report discusses some of the factor affecting the viability of a plan of frequency assignments for satellite broadcasting and shows that the data used by the planner leads logically to a regular distribution of channels, orbital positions and polarisations.
Keywords: orbital; antenna; channels; satellite; separation; mhz; channel; countries; polarisations; beamwidths; satellite broadcasting; orbital arc; orbital positions; receiving antenna; reference patterns; adjacent channels; countries sharing; orbital position; antenna reference; optimal distribution
Downloads: 34
[texts]BBC Research and Development Report Number 1976-28
R&D Report 1976-28 : Hadamard transformation: Assessment of bit-rate reduction methods. C.K.P. Clarke This report is concerned with the bit-rate reduction of signals produced by Walsh-Hadamard transformation of PCM television signals. The main characteristics of the transform signals are outlined and the methods of linear and non-linear coding used to reduce their bit rate are described. It was found that, with linear coding, a slightly higher bit rate is required to describe the transform coeff...
Keywords: transform; bits; coefficients; signal; coding; hadamard; errors; signals; impairment; sampling; subjective tests; coding system; colour bars; alphanumeric characters; bit rate; transform signals; signal energy; transform signal; test card; walsh functions
Downloads: 80
[texts]BBC Research and Development Report Number 1985-10
R&D Report 1985-10 : Digital audio editing G.W. McNally, P.S. Gaskell, A.J. Stirling New techniques are needed for reliable, fast and accurate editing of digital audio. The objective is to provide the facilities to which audio editors have grown accustomed while maintaining high operational speed and precise control, even when a tape is cut. Three levels of performance are discussed. The first and simplest is to cut the tape and use error concealment and electronic crossfading to smooth the spli...
Keywords: audio; data; editing; disc; rio; auxiliary; digital; edit; control; edits; audio editing; edit points; digital audio; high speed; auxiliary data; point location; signal processing; audio data; edit point; control panel
Downloads: 26
[texts]BBC Research and Development Report Number 1962-49
R&D Report 1962-49 : Multiplex systems for stereophonic broadcasting G.J. Phillips, J.G. Spencer This report discusses the various systems which have been proposed for broadcasting stereophonic programme from a single v.h.f. transmitter. The results of laboratory tests on two systems are summarized. The first is the Zenith-G.E. system, adopted in 1961 by the F.C.C. for stereophonic broadcasting in the U.S.A...
Keywords: stereophonic; subcarrier; monophonic; signal; reception; receiver; systems; system; modulation; multiplex; stereophonic broadcasting; working party; subcarrier system; multiplex systems; stereophonic reception; monophonic reception; monophonic listener; subcarrier systems; main carrier; subcarrier channel
Downloads: 30
[texts]BBC Research and Development Report Number 1969-18
R&D Report 1969-18 : Some observations on the application of optical spatial filtering techniques to motion picture printing E.W. Taylor A previous report (BBC RD 1968/41) considers the application of spatial filtering techniques to the process of down-printing from the 35 mm to the 16 mm film format. This present report considers the use of a graded filter in the Fourier plane and discusses the limitations in the use of this technique, in conjunction with an incandescent light source, for the e...
Keywords: film; spatial; exposure; transmission; source; radiation; filter; image; plane; fourier; graded filter; exposure time; fourier plane; spatial filtering; transmission factor; spatial filter; enhancement factor; light source; image plane; spatial frequency
Downloads: 26
[texts]BBC Research and Development Report Number 1975-09
R&D Report 1975-09 : A traffic information service employing time division multiplex transmissions. R.S. Sandell, M.W. Harman The use of broadcasting to provide traffic and road information to motorists continues to be developed, but there remain several problems. It would seem that a real improvement could be realised if it were possible to provide the driver with a service dedicated to his needs, but which would not overwhelm him with irrelevant data...
Keywords: traffic; field; receiver; strength; frequency; stations; mute; announcements; tdm; bbc; local radio; field work; field strength; protection ratio; protected field; motoring unit; time division; traffic announcements; service area; field strengths
Downloads: 25
[texts]BBC Research and Development Report Number 1984-18
R&D Report 1984-18 : Acoustic scaling: a re-evaluation of the acoustic model of Manchester Studio 7. R. Walker The reasons for the reconstruction and re-evaluation of the acoustic scale model of a large music studio are discussed. The design and construction of the model using mechanical and structural considerations rather than purely acoustic absorption criteria is described and the results obtained are given...
Keywords: acoustic; model; absorption; reverberation; scale; ventilation; frequency; studio; bbc; modelling; low frequency; full size; acoustic scale; ventilation trunking; reverberation time; scale model; audience seating; absorption coefficient; scale modelling; modular absorbers
Downloads: 26
[texts]BBC Research and Development Report Number 1976-12
R&D Report 1976-12 : Audio non-linearity: A comb-filter method for measuring distortion. R.A. Belcher A new method of measuring non-linear distortion of sound signals is described. This method uses a test-noise signal, based on a pseudo-random sequence and occupying most of the audio band, in conjunction with comb-filter techniques to measure distortion over a wide frequency range; it gives better correlation with subjective test results than the conventional total harmonic distortion method.
Keywords: distortion; test; signal; subjective; harmonic; impairment; frequency; method; circuits; measurement; test circuits; versus subjective; test signal; relative gain; total harmonic; distortion products; spectral gaps; subjective impairment; harmonic distortion; test method
Downloads: 44
[texts]BBC Research and Development Report 1956-38 : Low-power V.H.F./F/M. transmitters - Galashiels area site tests - C.J. White, D.W. Taplin, R.S. Sandell, J. Hall
R&D Report 1956-38 : Low-power V.H.F./F/M. transmitters - Galashiels area site tests. C.J. White, D.W. Taplin, R.S. Sandell, J. Hall Two sites were tested in the Galashiels area. It was found that Lindean Moor would provide the better service and this site is therefore recommended. Tests on the reception of television sound indicated the probability of a reliable signal from the Kirk o' Shotts v.h.f...
Keywords: lindean; strength; moor; shotts; dryden; site; aerial; field; transmitter; kirk; television sound; receiving aerial; field strength; ground level; lindean moor; area site; site tests; dryden hill; hill site
Downloads: 20
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